At Nottingham's bus station, one cold night last winter, a young West African girl was found wandering alone.

She said she had come from London, but was too frightened to say anything else and had no means of identification.

She was one of five children to turn up in this way, over a matter of months.

The children were put in the care of Anne Turner at Nottingham's social services department.

As they gained confidence a horrifying story emerged.

They told Ms Turner they had been kidnapped in Africa, by criminals, and sold into sexual slavery.

Traffickers had terrified the children into submission with a mixture of physical violence and rape, and the psychological threat of voodoo.

That frightening, almost surreal, story is a familiar one for Juliette Singer, of the national missing person's helpline.

She has helped to expose the trade in teenage girls from Nigeria to brothels in northern Italy, via Gatwick airport and West Sussex.

Lagos is part of the child trafficking route

Girls were turning up at the airport without documents and being put into care by West Sussex social services.

Police were only alerted when the girls started to go missing.

The mystery was solved when one of the girls turned up Italy, having claimed sanctuary in a church.

She told authorities that she and other girls had been picked up from local authority hostels, and taken overland to Italy.

On the way they were gang-raped and forced to sell themselves in lorry parks across Europe.

When they eventually arrived in Europe they were taken to brothels to work.

Disrupting the trade

I went to the campus of a college somewhere in London, to meet a girl who narrowly escaped that fate.

When she was 16, Comfort was lured to the Nigerian commercial capital Lagos by her uncle, and forced to work as a prostitute.

She was forced to have sex with up to six men a night.

Her uncle then decided to move Comfort and three other, older women to Italy.

They travelled via Gatwick, where Comfort was told to destroy her passport and make contact with a man who would take them on to Italy.

But Comfort was lucky - and brave.

She hid in the toilets, refusing to tear up her passport.

Then, when the coast was clear, she presented herself to immigration officials.

The social services departments that serve Gatwick and Heathrow airports have got wise to the tactics of the traffickers and in recent years have been able to disrupt their trade and help children like Comfort.

Comfort escaped by alerting authorities at Gatwick

But now it seems the traffickers have got wise too and they are diverting their victims to other cities.

In Newcastle more than 20 lone African children have turned up in the last six months.

The police are investigating the cases of eight children who have almost certainly been trafficked.

But the city's refugee service says that most are too scared to speak.

And in Nottingham, Anne Turner now believes the city has become an established route for the traffickers.

Now there is a need to raise awareness in other cities.

The traffickers are wily businessmen and have probably already moved on.

They thrive on the fear of their victims and the ignorance of the authorities.